1. Field of the Invention
The present invention relates to a data slicer and a method of driving the same, and more particularly to generation of reference voltage in the data slicer.
2. Description of the Background Art
There is a case of broadcasting, for example, where digital data is superimposed on a video signal input. In this case, a receiver of broadcasting needs to fetch the superimposed signal to decode the signal into digital data. Therefore, the receiver is provided with a data slicer.
A conventional (background-art) data slicer consists of a reference voltage generation circuit and a comparator circuit for comparing a reference voltage with an input signal. The reference voltage generation circuit generates a reference voltage on the basis of the input signal.
Specifically, when clock run-in of an input signal starts, an RC integration circuit included in the reference voltage generation circuit integrates the input signal. A value obtained by the RC integration circuit is a reference voltage.
The comparator circuit compares the obtained reference voltage with the input signal to take out a superimposed signal. Patent Document 1, Japanese Patent Application Laid Open Gazette No. 2001-189765, discloses this conventional data slicer.
The conventional data slicer has a problem of taking too much time to obtain the reference voltage since it uses the RC integration circuit to generate the reference voltage. In a case where an input signal quickly changes, particularly, the RC integration circuit can not follow this quick change and this arises a problem of not appropriately generating a reference voltage. Further, some of the conventional data slicers need a large capacity for holding the reference voltage outside the reference voltage generation circuit. For example, if the capacity used for the RC integration circuit is about 40 pF, the capacity provided outside is about 1000 pF. This disadvantageously increases the circuit scale of data slicer.